To determine the iodine value (IV) of sunflower oil, as well as perform a peroxide test, you can follow the outlined steps:
Iodine Value (IV):
The iodine value measures the degree of unsaturation in a fat or oil. It indicates the number of grams of iodine that can be absorbed by 100 grams of the oil. The higher the iodine value, the more unsaturated the oil is.
To determine the IV of sunflower oil, you can use the Wijs or Hanus method. Here's a simplified procedure using the Wijs method:
Weigh precisely 0.2 to 0.4 grams of sunflower oil into a clean and dry iodine flask.
Add 25 mL of Wijs solution (iodine monochloride solution) to the flask.
Swirl the flask to mix the contents and let it stand in the dark for around 30 minutes.
Add 10 mL of potassium iodide (KI) solution to react with any excess iodine.
Titrate the liberated iodine with a standardized sodium thiosulfate solution until the yellow color disappears.
Perform a blank titration without the oil to determine the iodine solution's background color.
Calculate the IV using the formula: IV = [(V1 - V0) × N × 0.0127] / W
V1 = volume of sodium thiosulfate solution used for the oil sample titration (in mL)
V0 = volume of sodium thiosulfate solution used for the blank titration (in mL)
N = normality of the sodium thiosulfate solution
W = weight of the oil sample used (in grams)
Peroxide Test:
The peroxide test measures the peroxide value (PV) in an oil sample, which indicates the degree of oxidation and rancidity. It determines the amount of peroxides (hydroperoxides) formed in the oil.
To perform the peroxide test, you can follow these steps:
Weigh precisely 5 grams of sunflower oil into a clean and dry test tube.
Add 30 mL of a solvent mixture, such as glacial acetic acid and chloroform (1:1).
Add a few drops of a saturated solution of potassium iodide (KI).
Close the test tube with a stopper and shake it vigorously for about one minute.
Allow the mixture to stand in the dark for about 5 minutes.
Titrate the liberated iodine with a standardized sodium thiosulfate solution until the yellow color fades.
Perform a blank titration without the oil to determine the iodine solution's background color.
Calculate the peroxide value (PV) using the formula: PV = [(V1 - V0) × N × 1000] / W
V1 = volume of sodium thiosulfate solution used for the oil sample titration (in mL)
V0 = volume of sodium thiosulfate solution used for the blank titration (in mL)
N = normality of the sodium thiosulfate solution
W = weight of the oil sample used (in grams)
To verify the hypothesis, you can compare the obtained iodine value (IV) and peroxide value (PV) of the sunflower oil with standard values. The standard values for sunflower oil may vary depending on the specific regulations or industry standards in your country. However, you can refer to recognized organizations like the American Oil Chemists' Society (AOCS) for typical ranges of IV and PV for sunflower oil. If the results fall within the expected range, it supports